A direct-type parking mechanism uses a wire connected to a shift lever to enable switching of a parking gear fastened to an output shaft of an automatic transmission between a rotatable unlocked state and an non-rotatable locked state. As an alternative, a shift-by-wire type parking mechanism has recently been developed that does away with the wire-to-gear mechanical connection by using an actuator connected to the parking gear to operate the gear.
During the process of parking, the shift-by-wire type parking mechanism needs more time than the direct type to switch from the unlocked state to the locked state. So when the gradient of the road surface the vehicle sits on is equal to or greater than a certain angle, the vehicle is liable to creep or roll down during parking and thus make it difficult for the parking wire to establish the locked state by pulling the parking pole.
Patent Reference 1 therefore proposes that at the time of putting the parking mechanism in the locked state, the vehicle's driven wheels be put in a non-rotating condition by, for example, automatic braking or operating the automatic transmission to generate driving force in the opposite direction from the torque inputted from the driven wheel side.